1. Field of the Invention
The present invention relates to a through anchor used for a seat belt device for an automobile.
2. Description of the Related Art
A webbing belt comprising a seat belt device for binding the body of a passenger seated on a seat of an automobile has one end in the longitudinal direction stopped on a winding shaft of a winding device provided on for example, the side of the seat, and the other end fixed on an anchor plate provided in the vicinity of the winding device. Moreover, the middle part in the longitudinal direction of the webbing belt is folded back to the downward direction above the winding device, for example by being placed through an inserting hole formed in a through anchor at the upper end side of a center pillar of the automobile.
The webbing belt is placed through an inserting hole of a tongue plate between the fold back part in the through anchor and the other end so that the webbing belt wound on the winding shaft of the winding device can be taken out by pulling the tongue plate, and the webbing belt can be mounted by interlocking the tongue plate with a buckle device provided on the side opposite to the winding device with respect to the seat.
Moreover, the above-mentioned through anchor comprises a metal mandrel with an original hole for the inserting hole formed. The part of the mandrel other than the part to be fixed on the center pillar of the automobile is molded with a synthetic resin material. Since the molded part is provided also in the original hole inner circumferential part of the inserting hole, the webbing belt is slid with respect to the molded part.
In consideration of taking out the webbing belt smoothly from the winding device, and taking up the webbing belt smoothly on the winding device, it is preferable that the friction between the through anchor and the webbing belt is small. As a means for reducing the friction between the through anchor and the webbing belt, a method of forming a resin piece made of a synthetic resin material such as a polyacetal (POM), and a high molecular weight polyethylene corresponding to the inner circumferential part of the inserting hole of the through anchor to be slid against the webbing belt, and forming a molded part with another synthetic resin material such as a nylon, with the resin piece in the state mounted on the original hole of the mandrel set in a mold, is conceivable.
However, when forming the molded part with a nylon, with respect to the molding temperature of 240xc2x0 C. at the time of molding, the melting point of the polyacetal is 165 to 175xc2x0 C., and the melting point of the high molecular weight polyethylene is 136xc2x0 C., and thus they are lower than the molding temperature. Therefore, since the resin piece made of the polyacetal or the high molecular weight polyethylene is melted or deformed at the time of molding, it has been extremely difficult to mold the molded part with the resin piece shape maintained.
In consideration of the circumstances, an object of the present invention is to obtain a through anchor capable of maintaining the good molding property and external appearance quality even when using a sliding member made of a synthetic resin material having a melting point lower than that the synthetic resin material providing the molded part, and a method for manufacturing such a through anchor.
According to a first aspect of the present invention, there is provided a method for manufacturing a through anchor comprising a mandrel made of a metal, a molded part made of a synthetic resin material, for covering the mandrel, with an inserting hole for inserting through a webbing belt formed, and a sliding member made of a synthetic resin material having a melting temperature lower than that of the synthetic resin material for forming the molded part, and a friction resistance of the external surface lower than that of the molded part, provided in the molded part corresponding to the sliding part of the inserting hole with respect to the webbing belt, comprising the steps of (a) forming a projecting part projecting from a cavity of a mold for molding the molded part, corresponding to the boundary part of the molded part and the sliding member on the external surface of the molded part and the sliding member, and (b) parting the sliding member and the synthetic resin material for forming the molded part injected in the mold by the projecting part in the vicinity of the external surface of the sliding member at the boundary part.
According to the method for manufacturing a through anchor of the above-mentioned configuration, the mandrel is set in the mold in the state with the sliding member mounted in a part corresponding to the sliding part of the through anchor with respect to the webbing belt in the mandrel. Then, the synthetic resin material is injected into the mold in this state. Thereby, the molded part is provided (hereinafter the synthetic resin material for forming the molded part is referred to as the xe2x80x9cmolding resinxe2x80x9d for the explanation convenience in order to distinguish the synthetic resin material for forming the molded part and the synthetic resin material for forming the sliding member).
Although the molding resin has a melting point higher than that of the synthetic resin material for forming the sliding member, since the projecting part is formed from the cavity of the mold corresponding to the vicinity of the boundary part of the sliding member with respect to the molded part at the external surface in the state with the sliding member and the molded part integrated, the projecting part is provided between the boundary part with respect to the molded part at the external surface of the sliding member and the molten molding resin in the mold so that the boundary part of the molded part at the external surface of the sliding member and the molten molding resin can be parted by the projecting part.
Accordingly, since the boundary part with respect to the molded part at the external surface of the sliding member is not contacted directly with the molten molding resin in the mold, the heat of the molten molding resin is not directly transmitted to the boundary part with respect to the molded part at the external surface of the sliding member. Thereby, at least at the time of molding the molded part, the boundary part with respect to the molded part at the external surface of the sliding member can hardly be melted.
Moreover, since the sliding member has a part with the molten molding resin and the sliding member directly contacted, the heat can be conducted from the synthetic resin material comprising the molded part at the part so as to partially melt the sliding member. However, since the boundary part with respect to the molded part at the external surface of the sliding member is contacted with the projecting part, even if the heat of the molten molding resin is transmitted to the vicinity of the boundary part with respect to the molded part at the external surface of the sliding member, it is discharged to the contacted projecting part, and thus the melting and deformation of the boundary part with respect to the molded part at the external surface of the sliding member can effectively prevented or restrained.
Furthermore, a groove is formed along the boundary part of the sliding member and the molded part at the external surface of the sliding member and the molded part, which are integrated after molding, owing to formation of the projecting part in the mold, with a fixing part of the sliding member and the molded part exposed at the bottom end part of the groove. Although the synthetic resin comprising the sliding member and the molding resin are mixed at the fixing part, since the fixing part is disposed at the bottom or end part of the groove without being exposed at the external surface of the sliding member and the molded part, the fixing part can hardly be seen from the outside so that the external appearance quality of the through anchor can be improved.
It is preferable that the method of the first aspect of the present invention further comprises a step of forming a bole communicating the sliding surface side of the sliding member with respect to the webbing belt and the side opposite to the sliding surface side in the sliding member, wherein the gas generated from the synthetic resin material comprising the molded part injected into the mold is discharged from the hole.
According to the method for manufacturing a through anchor of the above-mentioned configuration, a hole communicating the sliding surface side with respect to the webbing belt and the side opposite to the sliding surface (that is, the fixing surface side with respect to the molded part) is formed in the sliding member so that the gas generated from the molding resin at the time of molding is discharged to the outside through the hole.
Accordingly, in the method for manufacturing the through anchor, the gas generated from the molten molding resin is not contained in the vicinity of the fixing part of the sliding member with respect to the molded part, or the like, or the possibility thereof is extremely low. Thereby, the so-called voids (bubbles) by the gas cannot be formed after finishing the molding, or the possibility of the formation thereof is extremely low, and thus the molding failure or deterioration of the fixing performance derived from the voids can be prevented or restrained.
According to a second aspect of the present invention, there is provided a through anchor comprising a molded part made of a synthetic resin material, for covering the mandrel, with an inserting hole for inserting through a webbing belt formed, and a sliding member made of a synthetic resin material having a melting temperature lower than that of the molded part, and a surface friction resistance lower than that of the molded part provided in the molded part corresponding to the sliding part of the inserting hole with respect to the webbing belt. Furthermore, a groove opened in the surface of the molded part and the sliding member, with the boundary part of the molded part and the sliding member disposed in the inside thereof, is formed.
According to the through anchor of the above-mentioned configuration, the mandrel made of a metal is covered with the molded part made of a synthetic resin so that the webbing belt is inserted through the inserting hole formed in the molded part. Therefore, by mounting the through anchor on a predetermined position of an automobile (such as a center pillar), directly or indirectly, the middle part in the longitudinal direction of the webbing belt is supported by the through anchor (more specifically, by the inner circumferential part of the inserting hole).
Moreover, in the through anchor, the sliding member is provided in the molded part. Since the sliding member is provided corresponding to the sliding part of the inserting hole with respect to the webbing belt, friction is generated between the sliding member and the webbing belt at the time of taking out the webbing belt from the winding device storing the webbing belt in the wound state, or at the time of taking up the webbing belt onto the winding device. However, since the surface of the sliding member has a friction resistance lower than that of the molded part, resistance to the webbing belt is small at the time of taking out or taking up, and thus the webbing belt can be taken out or taken up smoothly.
In the through anchor, the sliding member is made of a synthetic resin material having a melting temperature lower than that of the synthetic resin comprising the molded part.
In the boundary part of the molded part and the sliding member or in the vicinity of the boundary part, the groove opened in the surface of the molded part and the sliding member is formed. Thereby, even if the molded part is formed by injecting a molten synthetic resin into a mold for molding the molded part with the mandrel set therein and the sliding member mounted on the mandrel, the boundary part of the molded part and the sliding member can be disposed inside the groove.
Therefore, the part with the synthetic resins comprising the molded part and the sliding member melted and mixed at the boundary can be hidden inside the groove. Thereby, even if the molded part is formed with the sliding member mounted on the mandrel, the quality of the external appearance can be improved (in other words, the molded part can be molded with the mandrel set in the mold for molding the molded part and the sliding member mounted on the mandrel without deteriorating the neat external appearance or the molding property).
Furthermore, a projecting part needs to be formed in the mold for molding the molded part, corresponding to the groove in providing the groove. Therefore, the sliding member is not contacted directly with the molded part at the boundary part with respect to the molded part in the surface of the sliding member, and thus transmission of the heat from the molten synthetic resin material comprising the molded part can be restrained. Furthermore, the heat transmitted from the synthetic resin material comprising the molded part melted by the contact with the projecting part in the mold for forming the groove can be discharged to the mold. Thereby, inadvertent melting or deformation of the sliding member can be restrained or prevented, and thus the molding property can be improved also thereby.
In the through anchor of the second aspect of the present invention, it is preferable that a hole communicating the part contacted with the molded part and the side opposite to the contacted part is formed in the sliding member.
According to the through anchor of the above-mentioned configuration, the hole is formed in the sliding member such that the part of the sliding member contacted with the molded part and the side opposite to the contacted part is communicated by the hole. Thereby, at the time of molding the molded part by injecting the molten synthetic resin material with the mandrel set in the mold for molding the molded part and the sliding member mounted on the mandrel, a gas or a moisture content generated from the air or the molten synthetic resin material in the mold cannot be blocked by the sliding member. The gas or the moisture content is guided to the opposite side with respect to the part contacted with the molded part of the sliding member through the hole formed in the sliding member. Furthermore, the gas or the moisture content is discharged to the outside of the mold.
Thereby, even though the molded part is molded with the mandrel set in the mold for molding the molded part and the sliding part mounted on the mandrel, generation of the molding failure, such as the voids (bubbles), burning, burr, or the like at the molded part can be prevented or restrained. In other words, the molded part can be molded with the mandrel set in the mold for molding the molded part and the sliding part mounted on the mandrel without deteriorating the neat external appearance or the molding property.